The invention refers to systems and a method for transporting brittle workpieces such as wafers made of brittle materials such as silicon, quartz, sapphire boron, etc., solar cells or any intermediate stage of wafer being processed into an end product such as solar cells thereof, according to the preamble of claims 1 and 23 respectively.

Such brittle workpieces are, e.g., wafers (the terms workpieces and wafers are used

interchangeably in this document) made of brittle materials such as silicon, quartz, sapphire boron, etc., solar cells or any intermediate stage of wafer being processed into an end product such as solar cells thereof. These workpieces are typically at least 30 μηη thick, even more preferably more than 60 μηη thick such as silicon wafer for solar cells that are typically 80-120 pm, sapphire sheets that are at least 0,2 mm thick. Even though such workpieces bend, they are brittle in the sense that bending too much will break them, not merely deform them.

Wafers, e.g. silicon wafers, use in solar cells or sapphire wafers used for led manufacturing are cut from a block (also called brick or ingot) in a wire cutting device employing a metal wire and abrasives. Usually abrasives suspended in slurry, that are transported by a metal wire, are used. Nowadays, wafers are cut more and more using fixed abrasives, which are directly attached to the metal wire. Such wire is e.g. called a diamond wire.

The ingot to be cut for solar cells may be poly-crystalline or mono-crystalline semiconductor material, e.g. silicon. Other materials such as sapphire may be cut as well. In the latter case, the ingot is generally referred to as core. The ingot is the base material the wafers are cut from. In the case of a poly-crystalline material, usually a large ingot is casted and bricks are cut from that. In case of a mono-crystalline material normally a round ingot is made for example using the Czochralski process and cut into the typical mono-crystalline wafer shape. Cores are drilled out of boule of sapphire. Cores are here also referred to as ingots. After (e.g. silicon, quartz, boron or sapphire) wafers have been cut, at first they normally remain attached to a beam. The beam is a piece of material holding the ingot at a distance of the wire saw, so that the cutting wire, that bends under the cutting action, do not cut into any machine parts. After having been cut, the wafers must be separated from the beam. Once this has been done, the wafers form a pile and need to be separated to be treated individually. Especially thin wafer, as thin as 100 or even 80 pm need to be treated very gentile. Small shocks or bending forces may lead to damage that renders the wafers worthless.

From DE102010006760 a system is known for separating wafers from pile. The pile is positioned in a wafer carrier and is submerged in a fluid. First and a second transporting means are used to remove the successive wafers from the pile and transport them in upward direction. Third, rotatable transporting means are used to bring the wafer into a horizontal position, so that it can be transported further by a normal conveyor belt.

US5213451A discloses an apparatus for separating semiconductor wafers from a wafer stack. The apparatus comprises a separating nozzle system releasing a liquid medium to lift off the uppermost wafer of the wafer stack and a conveying nozzle system releasing a liquid medium to push the uppermost wafer in a forward direction for leaving out of the wafer magazine. The wafer magazine is equipped with a feed unit which makes it possible to bring the uppermost wafer into the range of a separating nozzle system. The feeding unit moves the wafer stack upwardly, wherein the feeding direction is perpendicular to the wafer-plane of each wafer forming that stack. The wafers leave the separating apparatus over a dam. An apparatus for conveying the wafers in a horizontal plane adjoins that dam. The wafers are transferred from the conveying apparatus to a tray-filling apparatus. The wafer-plane of the wafers does not change during transition from the feeding unit towards the conveying apparatus and also not during transition from conveying apparatus towards the tray-filling apparatus.

The apparatus disclosed in US5213451A is not suited for separating wafers from a stack having a different shape and/or orientation, particularly where the wafer-plane of each wafer forming the stack is vertically aligned. Further, the risk of transferring together two or more wafers adhering to each other (over the dam) is very high.

WO2014012879A1 discloses a device for separating wafers from a wafer stack which is located on a support device in a liquid container. The support is equipped with an advancing device for continuously or incrementally advance the wafer stack. A bearing surface for the wafers in the wafer stack terminates at a sliding edge. A slideaway adjoins the sliding edge, said slideaway being oriented downwards. Nozzles generating a directed liquid flow are provided to force the uppermost wafer to leave the wafer stack in the direction of the slideaway.

The separating device disclosed in WO2014012879A1 is not suitable for wafer stacks in which the wafer-planes are vertically aligned. Although WO2014012879A1 proposes a sliding edge, the risk that two or more adhering wafers together leave the stack cannot be eliminated. In addition the edge poses a danger for the wafers that are particularly sensitive to forces working on their edges. WO2014012879A1 does not relate to a transporting system, in which singulated wafers are transported by a first transporting means one after another and then transferred to a second transporting means.

US2008146003A1 discloses a method for separation of a silicon wafer from a vertical stack of silicon wafers. The method comprises attaching a movable transport device to a surface of a silicon wafer in the stack. The wafer is then transferred by the movable transport device to a conveyor belt.

The object of the current invention is to provide a system for transporting flat brittle workpieces which is more cost-effective and which treats the wafers gentle. In addition the inventive system aligns the workpieces, making further treatment of the workpieces less complicated.

This object is achieved by a system and a method for transporting workpieces according to the features of claims 1 and 23 respectively.

According to the invention a system for transporting flat brittle workpieces is provided comprising a first transporting means for transporting the workpiece in upward transportation direction, this upward transportation direction preferably being mainly vertical, the first transporting means defining a first transporting plane, and a second transporting means for transporting the workpiece in a sideways transportation direction, this sideways direction preferably being mainly horizontal, an upstream portion of the second transporting means being located downstream of the first transporting means. Fluid flow generating means being provided for generating a fluid flow past the first transporting means and towards the second transporting means, preferably past a downstream end portion of the first transporting means.

The main advantage of the current invention over the state of the art is that the system is very cost-effective while still treating the wafers very gently. In Addition the system can be adapted to different workpiece sizes and materials. Moreover, the throughput of the system can be increased easily, provided the workpieces allow this, by increasing the speed of the transporting means and the power of the fluid flow generating means. This can be done by adapting the software of the controller. In addition the location and direction of the fluid flow generating means may be altered, which is still easy to do.

Moreover the fluid flow generating means generate a fluid flow intersecting with the first transportation plane and downstream of that first transporting means.

The fluid flow from the flow generating means may be directed by shielding or flow controlling means that influence the direction of flow. In this way less fluid can escape and the fluid flow may be less powerful thus further reducing resources needed (pressurized air, means for generating a string flow), while treating the wafers more gently. There are several possibilities to generate a fluid flow past the first transporting means and towards the second transporting means: A fluid flow may be generated behind (i.e. in the back of) the workpiece; the fluid flow generating means is arranged behind the workpiece and directs a fluid flow towards the flat surface of the workpiece (the workpiece is pushed over).

Alternatively, the fluid flow generating means may be a means for generating under-pressure: The fluid flow generating means may be arranged in front of the workpiece and the workpiece is attracted by the under-pressure. In a further alternative embodiment the fluid flow generating means may be arranged laterally of the workpiece (in a position before falling over); the fluid flow may cause - according to the Bernoulli principle (or according to the principle of a Venturi nozzle) - an under-pressure on the front side of the workpiece causing the workpiece to fall over.

In this document upstream indicates where the workpieces come from and downstream where they are transported to.

Preferably the upstream portion of the second transporting means is located adjacent, even more preferably directly adjacent the downstream end portion of the first transporting means.

In an embodiment the invention may be also understood as a system for transporting singulated flat workpieces one after another, wherein the transporting direction and (at the same time) the orientation of the wafers is changed with the aid of a fluid flow generating means. I.e. the first and second transportation direction are inclined with respect to each other and also the first and second transporting plane are inclined with respect to each other.

In a preferred embodiment of the invention the fluid flow generating means is a tilting means for tilting the workpieces (individually) from the first transporting plane to the second transporting plane. When a workpiece reaches the end of the first transporting means it is still oriented parallel to the first transporting plane (defined by the first transporting means). The tilting means - in form of a fluid flow generating means - causes the workpiece to fall over onto the second transporting means, i.e. the workpiece-plane (or workpiece surface) is tilted. Now the flat workpiece is oriented parallel to the second transporting plane (defined by the second transporting means). The tilting means according to the invention is a contact-less tilting means, since it does not directly touch the workpiece to be tilted; only the fluid flow generated by the tilting means comes into contact with the workpiece.

In a preferred embodiment of the invention the first transporting plane is essentially parallel to the first transportation direction and the second transporting plane is essentially parallel to the second transportation direction. This allows to transport individual, i.e. singulated, flat workpieces one after another and in the same plane allowing a space-saving construction. The plane of transport is (only) changed between the first and second transporting means by tilting the workpiece with the fluid flow generating means. Using other words: The workpieces are transported by the first transporting means with their workpiece-planes being essentially parallel to the first transportation direction (the workpiece- plane is parallel to the first transporting plane). With other words: the workpieces are transported laterally within the transport plane. Preferably, the workpieces are transported by the second transporting means with their workpiece-planes being essentially parallel to the second transportation direction (the workpiece-plane is parallel to the second transporting plane). The workpiece-plane is that plane in which the flat workpiece extends.

In a preferred embodiment of the invention the first transporting means and preferably also the second transporting means is/are adapted to transport the workpieces in a singulated manner one after another. I.e. transport of the workpieces may be performed subsequent to workpiece singulation.

In a preferred embodiment of the invention the system comprises a separation zone (preferably a fluid container), in which workpieces are singulated from a stack or pile of workpieces and wherein the first transporting means extends between the separation zone and the second transporting means. Such an arrangement allows to handle with differently shaped and/or differently orientated stack or piles, particularly a stack of vertically aligned flat workpieces. The first transporting means is adapted to transport the workpieces in a direction away from the separation zone and towards the second transporting means. The separation zone may be a separation station, a container, a support, etc.. It is important to note, that this embodiment allows to re-direct (i.e. change the transport direction of) the transport path of the already singulated workpieces.

Preferably, at least a substantial portion of the first transporting means, preferably the downstream end portion, preferably the overall conveyor belt portion of the first transporting means, is not submerged in a liquid, i.e. exposed to a gaseous (air) atmosphere. Preferably, the downstream end portion of the first transporting means and the upstream portion of the second transporting means are both not submerged in a liquid, i.e. exposed to a gaseous (air) atmosphere.

Preferably the first and second transporting planes including an angle larger than 70°, preferably larger than 80°, even more preferably largely about 90°. The second transporting plane extending either in upward or downward direction in the two first cases.

The first transporting means, having a workpiece holding surface, transports the wafer in upward direction, preferably mainly vertically. This workpiece holding surface may define the transporting plane at least near its downstream end. As the workpieces reach the end of that first transporting means, the portion for example ending because a conveyer belt of the first transporting means makes a sharp turn, the workpieces will disengage from the first

transporting means. The fluid flow, preferably a gas stream such as a stream of air, pressurized air or a protective gas, ensures that the workpieces fall over onto the second transporting means, preferably also containing a conveyer belt, that transports the workpieces further. The workpieces being transported on its, second workpiece holding surface. This second workpiece holding surface may define the second transporting plane at least near its upstream end.

The forces the workpieces are very small and diffuse. The large area of the workpiece and small weight ensure that a small pressure difference will have the desired effect of tipping it over. As the workpieces fall over, the air or gas in its way has to be displaced, providing an efficient cushioning of that fall and ensuring a soft landing. If this is not enough, additional means may be provided for generating a fluid flow against the workpiece in direction opposite to the direction it falls to. This means and fluid may have all features and properties as described in relation to the means for generating a fluid flow to tip the workpieces over. Barriers for air to flow away may also be used. To make the workpiece fall over more quickly, the surface it falls onto, for example the transporting means, may be porous, have holes in it or even suction means may be provided.

As was stated above, the first transporting means may transport the workpieces in mainly vertical direction. Mainly vertical meaning in a direction making an angle with the vertical smaller than 30°, preferably smaller than 15°, even more preferred smaller 5° such as about 0°.

The first transporting means may contain a portion of a conveyer belt that transports the workpieces in mainly vertical direction. The conveyer belt typically extending all the way to the region where the workpieces fall over. The portion may even extend over a curved portion of that belt, where the surface holding the workpieces changes direction. The second transportation means transports the workpieces further in a sideway direction after they have left the first transporting means. Sideways meaning that the workpieces are no longer transported mainly in vertical direction but in a mainly horizontal direction. This second direction typically making an angle with the horizontal smaller than 30°, preferably smaller than 15°, even more preferred smaller 5° such as about 0°.

The any of the first, second or third transporting means may comprise a conveyer belt portion a conveyer belt. Here, the surface of the belt defines the transporting plane. The first transporting means and the second transporting means may in fact comprise or be formed by one conveyer belt, for example having a surface for supporting wafers that is L- shaped, portions thereof preferably extending in the first and second transporting direction.

The first and second conveyor belt portions may for example be part of individual conveyer belts. It is especially preferred that the first conveyor belt portion and the transporting means are part of one single conveyer belt. In that case this single conveyer belt may be L -shaped.

The first, second and third transporting means or any combination thereof may be any suitable transporting means such as a conveyer belt, a water track (as known for example from WO 94/0239, Fluid transport system for transporting articles, Minnesota mining and manufacturing company), or even a robot arm and may differ from each other.

The wafers normally are located in a, possible submerged, wafer carrier. As they are

transported upward, their orientation on the first transporting means is rather undefined.

According to the state of the art this misalignment is passed on to the second transporting means. Since the error can be quite large, the subsequent alignment unit needs to be able to deal with this. According to the current invention, the wafers are aligned while being transferred from the first transporting means to the second transporting means, as will be explained next.

As the workpieces are moved upward by the first transporting means and start to extend beyond the end portion thereof, the wafers are about to fall. Moreover, as the first transporting means can no longer hold them, they are free to fall. However, before the wafers fall, the means for generating a fluid flow in a tipping direction are employed (or are already running in a continuous mode) to tip them in the preferred direction: towards and onto the second

transporting means. The modest fluid flow in combination with the air that needs to be pushed aside for the wafer to fall over makes that the wafer fall over gently.

If the first transposing means contains a conveyer belt portion, the lower portion of the workpieces, as they fall over, is transported along with a first conveyer belt's curved end portion. Depending on the speed of the first transporting means, the wafer may momentarily leave the first transporting means all together and momentarily "fly" to the second transporting means. As the wafer temporarily stands on its lower edge (possibly after having travelled through the air), its orientation is aligned with the wafer holding surface of the second transporting means, defining its orientation around the horizontal axis. Moreover, the lower edge of the wafer now extends perpendicularly to the first transportation direction and in the plane of the wafer holding surface of the second transporting means. After falling over, the workpiece lies on the holding surface of the second transporting means and its position and orientation are very well determined.

In order to protect the workpiece from air currents and the like, shielding may be provided to ensure that conditions are always the same and only the means for generating a fluid flow determine how the workpiece falls.

It was found that depending on the velocity of the workpieces, the falling-over may introduce a small rotation about the central axis of the workpiece (extending perpendicularly to the surface of the workpiece and after having fallen over on a horizontal conveyer belt of the second transporting means pointing vertically upward). Therefore the wafers are now almost perfectly oriented, still making it much easier to align them properly by a next unit. As will be described later, small rotation about the central axis can be counteracted by having suction holes in the second transporting means.

Once manufactured, solar cells are commonly shipped in stacks or piles. According to the state of the art, cells are normally de-stacked while the pile extends in vertical direction. The current invention may be used for de-staking solar cells as well. In that case the pile of cells would be places to extend at least diagonally or even more or less horizontally. A suction band can now take the wafers from the pile and transport and align them as described above.

Separation fluid nozzles may be provided that aim a stream of fluid (say water or air) from the side toward the pile. Moreover, in the transversal direction the workpieces. This helps to remove them from the pile.

Preferably the first transporting means comprises a first conveyer belt portion and optionally further comprises a third conveyor belt portion being provided upstream of the first conveyer belt portion. The third conveyor belt portion may have other properties than the first conveyor belt portion. It may for example be suited for collecting and holding workpieces underwater.

Workpieces in a fluid filled container may thus be engaged and transported to the first conveyor belt portion.

Preferably a fluid container is provided, wherein preferably the third conveyer belt portion at least partially extends into with its lower portion. In that way wafers in the system may be submerged in water, thus preventing them from drying out. If any of the transporting means comprise a conveyer belt or a conveyer belt portion, the transporting means may be realized in a cost effective manner. Preferably any of the first transporting means, the second transporting means, the third transporting means or any combination thereof at least partially comprising a suction belt for better holding the workpieces.

Moreover, only a portion of the conveyer belts may be provided with means to form a suction belt. For example the third conveyer belt may be a suction belt to take the workpieces from the pile and hold them while moving them though the fluid in upward direction. If the third conveyer belt extends above the fluid level, adhesive forces may in that portion above the fluid level hold the wet workpiece on the holding surface without the need of underpressure. Moreover, the first conveyer belt may near its upper or upstream end not be a suction belt but a normal conveyer belt. The third conveyer belt may be a suction belt, preferably essentially over its complete length in order to better separate the workpieces from the pile.

The second transporting means may be or comprise a conveyer belt or a conveyer belt portion. If needed it may be a suction belt, for example with suction means in a downstream portion where the workpieces fall onto the transporting means, thus, as was previously described, fixating its orientation after it has fallen over. Once the orientation is fixed, and the workpiece has no kinetic energy other than what is associated with the movement of the conveyer belt, the workpiece needs not to be held and no underpressure is needed any more. Moreover, as the workpiece has to leave this belt, it probably is beneficial if it does not extend over a part of the conveyer belt that is a suction belt so that the workpiece can be moved off the belt more easily. The first conveyer belt portion, the third conveyer belt portion, the second transporting means or any combination may be part of a conveyer belt. As the workpieces travel in upward direction, they eventually come to the end of the first conveyer belt portion and fall over. In order to let the workpiece fall on a flat surface, the first conveyer belt portion and the second transporting means may be part of one single conveyer belt. The upper portion of the first transporting means and the workpiece holding surface of the second transporting means preferably form one flat plane for the workpieces to land on. It may or may not be interrupted. The former for example being the case when the first conveyer belt portion and the second transporting means are two separate conveyer belts, the latter when the two are part of one conveyer belt. Preferably the first transporting means mainly extends below the second transporting plane, preferably the first transporting means reaching mainly to this second transporting plane, so that workpieces fall over more gently. Preferably the spraying angle of the fluid flow generating means lies in the range of 30° to 60°, preferably from 40° to 50°.

Preferably the first transporting direction (F) and second transporting direction (S) include an angle between 70° and 120°, preferably between 80° and 100°, even more preferably between 85° and 95° such as about 90°. In this way the workpieces can make an appreciable turn.

Preferably a fluid centre axis of the fluid flow generating means is located at a distance of 5 to 30 mm, preferably about 10 to 20 mm, above downstream end portion of first transporting means, measured in the first transporting direction and in the first transporting plane.

The fluid flow centre axis is the axis best representing the direction of the fluid flow, located near its centre. Preferably the fluid flow centre axis extends mainly in a vertical plane so that no asymmetrical forces act on the workpieces making it rotate in any other direction than the tipping direction.

In this way the torque or moment of force acting on the workpieces is large enough to surely make it fall in the right direction. On the other hand, engaging the wafer further from its lower edge, would bend the wafer more than needed, thus augmenting the danger of damaging the workpiece.

Preferably the fluid centre axis of the fluid flow generating means includes an angle of about 50° to 90°, preferably about 70° to 85° with the first transporting plane, the fluid centre axis pointing in upward direction. Moreover, the fluid flowing in upward direction. It was found that aiming the fluid flow upwards ensures that the wafers fall over more easily. If multiple flow generating means are used, the centre axis is the centre axis of the flow field generated. The angle being the smallest angle between the fluid flow centre axis and a plane holding the workpiece holding surface.

Preferably the fluid flow generating means are located at a distance less than 60 mm, preferably less than 50 mm, away from the first transporting plane of the first transporting means, measured in in the second transporting direction, in this way the fluid flow engages a larger area of the wafer, thus preventing localized large forces and stresses.

Preferably the fluid flow generating means contain means selected from the group consisting of a nozzle, preferably for pressurized air, a propeller, a fan, a duct for under-pressure or any combination thereof, preferably multiple instances of these means being provided respectively (each element of this group may or may not be present and may be provided once or multiple times). If multiple means for generating a fluid flow are present, they may be controlled individually, for example by a controller or they may for example be p re-set as to deliver different flows of fluid to the workpiece. For example a nozzle generating a flow higher up on the workpiece may generate a faster or more forceful flow than a nozzle generating a flow impinging on a lower portion of the workpiece. The means for generating a fluid flow may thus provide a more or less uniform pressure over larger regions of the workpiece, thus minimizing the local tension in the workpiece. Moreover, the number and type of means for generating a fluid flow are chosen and controlled to minimize the impact on the workpieces, during tipping over and during "landing".

Preferably a controller is provided for controlling any element selected form the group consisting of the first transporting means, the second transporting means, the third transporting means, the fluid flow generating means or any combination thereof. In this way the means for generating a fluid flow may be turned on and off at appropriate times, for example when a wafer arrives. Also the transporting means may be turned on just before workpieces arrive or their speeds may be adjusted (dynamically) to the workpieces. Sensors maybe used for detection the presence and type of workpieces.

Preferably the speed of the fluid flow generated by the fluid flow generating means is a function of the speed of the first transporting means, the speed of the fluid flow preferably being larger than the speed of the first transporting means. For workpieces like wafers, the speed of the first transporting means lies between 0.1 and 1 m/s, preferably between 0.1 and 0.5 m/s.

In this way workpieces fall over the right way and land on the second transporting means in a gentle way. The fluid may have an average speed between 0.1 and 300 m/s, preferably between 1 and 200 m/s and even more preferably between 10 and 150 m/s.

The speed of the fluid flow being defined as the speed of the fluid as it leaves the means for generating a fluid flow.

In order to make the workpieces fall over, the force acting on them as a consequence of the fluid flow must accelerate its upper edge more than the lower is accelerated as result of the velocity of the first transporting means. Note that even though the first transporting means may have a constant velocity, the lower edge is still accelerated: the lower edge of the workpiece has at first no horizontal speed and in the end has a significant larger speed in that direction (assuming the first transporting means extends vertically and the second transporting means extend horizontally). Therefore the lower edge is accelerated. The fluid flow must give the upper edge (that initially has no horizontal speed) an acceleration that is larger than that of the lower edge in order to make the workpiece fall over the right way. In order to make the force for accelerating the upper edge to a high enough degree, the fluid flow must be fast enough. Put differently: the fluid flow from the fluid flow generating means must exert a larger torque of the wafer than the air the latter has to push aside in order to fall over.

In a further aspect of the invention a method is provided for transporting wafers with a system as previously described. Preferably, the workplaces are transported by the first transporting means in a singulated manner one after another. I.e. the workpieces are already singulated when being transported by the first transporting means. The invention therefore provides a system of transporting singulated workpieces and changing their transporting direction (with the aid of a fluid flow generating means). Preferably, the workpieces are transported by the first transporting means with their workpiece- p!anes being essentially parallel to the first transportation direction. This embodiment allows a space-saving design and safe transport.

As used in this document, "means" always refers to both singular and plural instances of those means. Further embodiments of the invention are indicated in the figures and in the dependent claims. The list of reference marks forms part of the disclosure. The invention will now be explained in detail by the drawings. In the drawings:

Figs. 1 through 4 show how a wafer is taken from ta pile of wafers and deposited onto conveyor means; Figs. 5a through 5d show how a wafer falls over as it is transferred from the first vertical conveyor belt to the horizontal transporting means;

Fig. 6 shows an alternative embodiment; and

Fig. 7 shows a further alternative embodiment.

Fig. 1 shows an embodiment of a transport system 1 according to the invention. Shown is a pile or stack 2 of workpieces, here wafers 3, held by holding means 6 in a fluid container 5. The stack 2 of wafers is submerged in a fluid 7 with a fluid level 8 above it. The wafers 3 have just been cut from for example an ingot, brick or core, for example using a multi wire saw (not shown). After that the beam holding the single workpieces has been removed, the workpieces are stil! in the carrier and now need to be separated in order to be treated individually. The wafers 3 may for example be slices of silicon, boron, quartz or sapphire. All these materials are be sliced and processed in more or less the same way. First transportation means 10 consist of a first conveyer belt with a first workpiece holding surface 18. Suction means 27 make conveyer belt 10 near its bottom end a suction belt.

Second transporting means 12 also is a conveyer belt and comprises a conveyer belt portion 12' and has an upstream portion 19 adjacent first transportation means 10. It transports workpieces in transporting plane 25.

As shown in figure 1 , the foremost wafer 4 of the stack 2 of wafers is too far away from third conveyer belt 11 , here a suction belt, to be transported off. The holding means 6 move (moving means not shown) the stack 2 of wafers towards the third conveyer belt 1 1 so that the fluid flow 30 from the separation fluid nozzles 13 separates the foremost wafers 4 from the pile 2. The wafers 3 only need to be separated over a very small distance so that fluid 30 can flow between the wafers 3 as the foremost wafer 4 is engaged and transported off by the third conveyer belt 1 1. This is shown in figure 2.

Referring to figure 1 , suction means 26 and 27 are shown that make a portion of respective the third conveyer belt 11 and first conveyer belt 10 to a suction belt. Suction means 26 suck in fluid 7 through holes (not shown) in the third conveyer belt 11 , thus engaging the foremost wafer 4.

The first 10' and third 11' conveyer belt portions of respectively the first conveyer belt 10 and third conveyer belt 11 are used to transport the wafers 3 in the first transporting, here vertical, direction F. The second transporting means 12, here also a conveyer belt transports the wafers 3 on a second workpiece holding surface 37 in the second transporting direction, here horizontal, direction S.

The wafer 3 is transported in first transporting direction F on the first holding surface 18 of first conveyer belt portion 10', this first surface 18 extending in a first transporting plane 24. The fluid flow 15 is generated as to intersect with this first transporting plane 24, downstream of first conveyer belt portion 10', preferably under an angle a smaller than 90°. As the wafers 3 are held in the downstream end portion 22 of first conveyer belt portion 10', extending above that end portion, the fluid flow 15 exerts a force on them.

As can be seen from figure 1 , first transporting direction F and second transporting direction S make an angle of approximately 90°. This angle can also for example be smaller, in which case the second transporting means would run in downward direction. As can be seen from the figs, the first transporting plane 24 is essentially parallel to the first transportation direction F and the second transporting plane 25 is essentially parallel to the second transportation direction S. The workpieces 3 are transported by the first transporting means 10 with their workpiece-planes being essentially parallel to the first transportation direction F. The same holds for the second transporting means 12 and the second transporting direction S.

The first transporting means 10 and the second transporting means 12 are adapted to transport the workpieces 3 in a singulated manner one after another. The system 1 comprises a separation zone, in which workpieces 3 are singulated from a pile or stack 2 of workpieces 3. In the present embodiment the separation zone is a fluid container 5. The first transporting means 10 extends between the fluid container 5 and the second transporting means 12.

The upstream portion 19 of the second transporting means 12 is located adjacent the downstream end portion 22 of the first transporting means 10. Shown in figure 1 is that the first 24 and second 25 transporting planes including an angle β of about 90°.

!n figure 2 a wafer 3 is engaged by the third conveyer belt 1 1 that transports it in the first transporting direction F.

As the wafer 3 is transported further, the first conveyer belt 10 takes it over and transports it even further. In order to pull the wafer 3 from the third conveyer belt 11 , the first conveyer belt 10 has suction means 27 to firmly grip wafer 3.

Once the wafer 3 has been transported out of fluid 7, the wafer 3 will stick to the first conveyer belt 10 by means of adhesion forces only, as is shown in figure 3. Therefore the suction means 27 are only provided near the lower or downstream portion 32 of the first conveyer belt 10. In figure 4 wafer 3 reaches the top 33 of first conveyer belt portion 10' and comes under the influence of the fluid flow generating means 14 generating fluid flow 15. As wafer 3 is transported further, the fluid flow 15 makes it fall over onto conveyer belt portion 12' of the second transporting means 12.

Figures 5a through 5d show the tipping over of wafer 3 in detail. As the wafer 3 is transported upward by the first conveyer belt 10, it is held by the adhesive forces of the fluid 7 (not shown) between the wafer 3 and the first conveyer belt 10 only. As it travels upward, it comes under the influence of fluid flow 15 and falls over.

As can be seen in figure 5b, at first the lower wafer edge 6 remains on first conveyer belt portion 10'. If the lower wafer edge 16 makes an angle relative to the surface of the first conveyer belt portion 10', the wafer 3 will move so that its lower edge becomes aligned with the surface of the first conveyer belt portion 10'. This is illustrated by the lower wafer edge 16 being visible in figures 5a and to a slightly less extend in 5b, while not being visible in figures 5c and 5d.

Fluid flow 15, preferably pressurized air coming out of nozzles (not shown), ensures that the wafer 3 falls in the right direction. As long as the wafer 3 overlaps with part of the first conveyer belt portion 10', it is more or less attached thereto. Once only a small or no overlap is left, the wafer 3 can fall over, depending on parameters such as the force exerted by the fluid flow 15 on the wafer 3, the speed the wafer 3 has, its mass and the fluid 7 used.

As the lower edge 16 of the wafer is moved to the right in the drawing, the wafer 3 will normally rotate counter-clockwise and fall in the wrong direction, since a torque acts on the wafer 3 making it turn that way. According to the invention the fluid flow 15 makes the upper edge 17 move to the right faster than its lower edge 16 is, thus tipping it over towards the horizontal conveying belt portion 12' (not shown in figures 5).

As wafer 3 falls over, it has to push the ambient air 31 out of its way. This cushions the fall and ensured a benign landing. As can be seen particularly from figs. 5a to 5d fluid flow generating means 14 is a tilting means for tilting the workpieces 3 from the first transporting plane 24 to the (inclined) second transporting plane 25.

Figure 6 shows an alternative embodiment in which first conveyer belt portion 10' (having first workpiece holding surface 18) and second transporting means 12 are integrated in one L- shaped conveyer belt 21. The advantage of this embodiment lies in the fact that there is no gap 9 (as shown in figure 1 ) between the first conveyer belt portion 10' and the second transporting means 12. A gap 9 enables ambient air 31 (figures 5a-5d) to be pushed away more easily, thus reducing the cushioning effect. In addition, the surface the wafer 3 lands on is more even in this embodiment. Fourth transporting means 34, here a conveyer belt, are shown for transporting the wafer further.

In the embodiment of figure 6, suction mean 28 are shown that hold the wafer 3 directly after it tipped over, thus ensure even better alignment.

Also shown in figure 6 is flow controlling means 38 that help aim the fluid flow 15 towards the wafer 3" when it has to be tipped over. Such flow controlling means 38 can prevent fluid from escaping and the fluid flow may be less powerful thus further reducing resources needed (pressurized air, means for generating a string flow), while treating the wafers more gently. Figure 7 shows a further alternative embodiment. Here the second transporting means 12 are located on the other side of the first transporting means 10 as compared to the previous embodiments. Like with the previous embodiments, fluid flow 15 extends over the first conveyor belt surface portion 10' and towards the second transporting means 12, making an angle a with first transporting plane 24 or a plane 24' parallel thereto.

As can be seen in figure 1 , the fluid generating means 14, the first, second and third

transporting means and suction means 26, 27 may be connected to a controller 35 by electrical conductors 38. This applies mutatis mutandis to ail embodiments shown as well as to the system described in the claims. The invention is not restricted to these embodiments. Other variants will be obvious for the person skilled in the art and are considered to lie within the scope of the invention as formulated in the following claims.

List of reference marks

1 System for transporting workpieces 21 L-shaped conveyer belt

2 Pile or stack of wafers 22 Downstream end portion

3 Wafer .23 Fluid centre axis

4 Foremost wafer 24 First transporting plane

5 Fluid container 24' Plane parallel to plane 24

6 Holding means 25 Second transporting plane

7 Fluid 26 Suction means

8 Fluid level 27 Suction means

9 Gap 28 Suction means

10 First transporting means 29 Upstream

10' First conveyer belt portion 30 Fluid flow

1 1 Third transporting means 31 Ambient air

1 1 ¹ Third conveyer belt portion 32 Lower or downstream portion

1 1 " Lower portion of third conveyer 33 Top of first suction belt portion 10' belt portion 34 Fourth transporting means

12 Second transporting means 35 Controller

2' Conveyer belt portion of second 36 Electrical conductors

transporting means 37 Second workpiece holding surface

13 Separation fluid nozzles 38 Flow controlling means

14 Fluid flow generating means

15 Fluid flow a Angle between wafer and centre axis

16 Lower wafer edge F First transporting direction

17 Upper wafer edge S Second transporting direction

18 First workpiece holding surface d Direction of flow

19 Upstream portion D Distance between centre of fluid flow

20 Downstream and first vertical conveyer belt